[FFmpeg-devel] [PATCH 1/2] libavcodec/zmbvenc: block scoring improvements/bug fixes

[Carl Eugen Hoyos]

2019-02-21 11:26 GMT+01:00, Tomas Härdin <tjoppen at acc.umu.se>:
> ons 2019-02-20 klockan 23:33 +0100 skrev Carl Eugen Hoyos:
>> > 2019-02-10 16:42 GMT+01:00, Tomas Härdin <tjoppen at acc.umu.se>:
>> > lör 2019-02-09 klockan 13:10 +0000 skrev Matthew Fearnley:
>> > > - Improve block choices by counting 0-bytes in the entropy score
>> > > - Make histogram use uint16_t type, to allow byte counts from 16*16
>> > > (current block size) up to 255*255 (maximum allowed 8bpp block size)
>> > > - Make sure score table is big enough for a full block's worth of
>> > > bytes
>> > > - Calculate *xored without using code in inner loop
>> > > ---
>> > >  libavcodec/zmbvenc.c | 22 ++++++++++++++++------
>> > >  1 file changed, 16 insertions(+), 6 deletions(-)
>> >
>> > Passes FATE, looks good to me
>>
>> I believe you asked on irc about fate tests:
>> Since such a test would depend on the zlib version, you cannot test
>> exact output, you could only test a round-trip (assuming the codec
>> really is lossless).
>
> Right, we'd need to embed a specific version of zlib. But we probably
> don't want to do that, for many reasons.
>
> A dummy DEFLATE implementation that just passes the bytes along could
> be useful. I know there's a mode in the DEFLATE format for blocks that
> fail to compress. That way we could test many encoders that depend on
> zlib, and their output should decode just fine.

What's wrong with a round-trip test?

Carl Eugen